The present invention relates to the textile industry and in particular to an improved machine for controling heddle frames and permitting introduction of weft threads into the shed from one side of a loom.
The invention shall especially be described for the case where a weft thread is to be inserted in the shape of a loop. The invention, however, is not limited to this weft thread insertion technique and could be utilized with other types of looms such as looms which use a shuttle.
The insertion of a weft thread in the shape of a loop is an old technique which was abandoned, especially in fast looms, because abnormal tensions were produced as a result of the friction of the thread against the insertion device pin. However, means such as a controlled rotation of the insertion device pin were designed to avoid such friction. Another type of means to avoid such friction is described in French Pat. No. 1,562,147; according to this document, the thread is cast in the shape of a loop with one locked strand, while the other strand is cast. The kinetic energy of the cast strand which is transferred to the locked strand through the loop, changes into a force which moves with the loop and pulls the thread.
As indicated in the article published in the periodical "L'Industrie Textile," Issue No. 1083, November 1978, pp. 698-699, with an inertia insertion system where the locked strand is resting at the entrance to the shed before the loop reaches the exit point it is theoretically possible to start closing the shed and firmly pushing the thread at the entrance, before the pick of weft thread is completely unwound. This closing of the shed at the insertion side of the loom before the weft thread reaches the exit point may be performed by using rigid frames to control the heddles. Each end of these frames should move in a different pattern, such that the shed has a correct opening along the whole section where the free strand of the loop is moving, during the loom cycle, and closes up along the section of the pick of weft thread formed by the locked strand. The tightening of the pick of weft thread may be performed by means of a reed where each end of this reed moves in a different pattern, or else by means of a rotating reed which offers the advantage of being less noisy than a regular reed.
This solution which consists in providing for a different pattern of motion of each end of the heddle-holder frames controlling the warp threads, presents a disadvantage in that the heddles in conventional heddle frames wear out very rapidly in the heddle-holder rods, due to the lateral motion of the heddle-holders as a result of the variable inclination of the frames.
It has also been suggested in the German Pat. No. 1,091,949 to have each frame move in a differing pattern in weaving looms fed by a griff throwing system in the shape of a strip, the length of which is equivalent to the width of the material, in order to minimize the disadvantage of an opening larger than the shed resulting from such an insertion procedure. To that effect, the loom is equipped with a rigid stationary frame in which the heddle-holder rods, together with the heddles, each move in a different pattern. The motion is transmitted to the heddler-holder rods by plates guided in the stationary frame and driven by a rigid beam which is controlled at each end by two eccentrics each one moving in a differing pattern.
In such a design the shed moves so that the crossing of the warp threads moves along the shed as in the case of waving-shed looms. However, it presents some disadvantages, and especially the disadvantage of requiring more space in height than the classical frames, as well as of necessitating a considerable number of connections which wear out rapidly.